Gas separation is useful in many industries and can typically be accomplished by flowing a mixture of gases over an adsorbent material that preferentially adsorbs one or more gas components in a feed stream, while not adsorbing one or more other gas components. The non-adsorbed components are recovered as a separate product. The separation of gas components by adsorption is a conventional approach that is performed in a variety of approaches. For example, adsorptive separations may be based on the differences in equilibrium affinities of the various gas components (e.g., equilibrium separations) or on the differences in adsorption kinetics of the gas components (e.g., kinetics separations).
One particular type of gas separation technology is swing adsorption, such as temperature swing adsorption (TSA), pressure swing adsorption (PSA), partial pressure swing adsorption (PPSA), rapid cycle pressure swing adsorption (RCPSA), rapid cycle partial pressure swing adsorption (RCPPSA), and not limited to but also combinations of the fore mentioned processes, such as pressure and temperature swing adsorption. As an example, PSA processes rely on the phenomenon of certain gas components being more readily adsorbed within the pore structure or free volume of an adsorbent material when the gas component is under pressure. That is, the higher the gas pressure, the greater the amount of readily-adsorbed gas adsorbed. When the pressure is reduced, the adsorbed gas component is released, or desorbed from the adsorbent material.
The swing adsorption processes (e.g., PSA and TSA) may be used to separate gas components of a gas mixture because different gas components tend to fill the micropore of the adsorbent material to different extents. For example, if a gas mixture, such as natural gas, is passed under pressure through an adsorbent bed unit, which may referred to as adsorption bed unit or vessel, containing an adsorbent material that is more selective towards carbon dioxide than it is for methane, at least a portion of the carbon dioxide is selectively adsorbed by the adsorbent material, and the gas exiting the adsorbent bed unit is enriched in methane. When the adsorbent material reaches the end of its capacity to adsorb carbon dioxide, it is regenerated by reducing the pressure, thereby releasing the adsorbed carbon dioxide. The adsorbent material is then typically purged and repressurized. Then, the adsorbent material is ready for another adsorption cycle.
The swing adsorption processes typically involve adsorbent bed units, which include an adsorbent material disposed within the housing of the adsorbent bed unit. These adsorbent bed units utilize different packing material in the adsorbent bed structures. For example, the adsorbent bed units utilize checker brick, pebble beds or other available packing. As an enhancement, some adsorbent bed units may utilize engineered packing within the adsorbent bed structure. The engineered packing may include a material provided in a specific configuration, such as a honeycomb, ceramic forms or the like. The engineered packing may be formed from the adsorbent material or may be a coating on a structure or support.
Further, various adsorbent bed units may be coupled together with conduits, manifolds and valves to manage the flow of fluids. Orchestrating these adsorbent bed units involves coordinating the cycles for each of the adsorbent bed units with other adsorbent bed units in the system. A complete cycle can vary from seconds to minutes as it transfers a plurality of gaseous streams through one or more of the adsorbent bed units.
However, swing adsorption processes present certain challenges because of several demanding technical factors, such as rapid cycle adsorption processes. These factors may include maintaining a low pressure drop through the adsorbent bed, good flow distribution within the adsorbent bed and minimal dispersion (e.g., axial spreading) of the concentration front in the adsorbent bed. Also, another factor may include a rapid cycling time that in turn requires fast acting and low dead-volume valves. Finally, another factor may be that an adsorbent bed unit should be configured to contain the adsorbent bed at certain pressures, to support the fast acting valves, and to minimize the dead volume within the adsorbent bed unit.
These challenges are even more complicated for processes with very high volumetric flows. A typical rapid cycle adsorbent bed unit is configured as a vertical cylinder with flat endplates (heads) for minimizing dead volume. Flow enters and exits the adsorbent bed unit through fast-acting valves mounted on the flat heads adjacent to the adsorbent material. The requirements for flat heads and high design pressures introduce practical limitations to the adsorbent bed diameter. For example, for a maximum working pressure of 85 bar absolute (bara), the practical maximum adsorbent bed unit inside diameter is approximately 1.4 meters (m), and the corresponding flat head thickness is approximately 355 millimeters (mm) to 380 mm. The fatigue life and cyclic deflection of the head is strongly influenced by the number and sizes of bores through the head for the valves. As such, the number and size of the bores through the head is a limiting factor in the design of an adsorbent bed unit.
Yet, the footprint (e.g., surface area) available on top of the adsorbent bed unit adjacent to the adsorbent bed may not accommodate the valves. For example, adsorbent beds may have cylindrical forms to present a circular cross-section area to the streams entering the adsorbent bed unit, where the valves are installed. The valves themselves have a similar footprint, which is also circular. As such, even when these valves are packed closely, a sizeable amount of footprint on top of the adsorbent beds is inaccessible for installation of the valves. Thus, the conventional bed structures do not accommodate valves for various configurations.
Accordingly, there remains a need in the industry for apparatus, methods, and systems that provided enhancements to manage the flow of fluids to the adsorbent beds. The present techniques overcome the drawbacks of conventional swing adsorption approaches by using oversized heads to provide flow paths for the gas volumes. This present techniques provide a lower capital investment, much smaller equipment foot-print, and lower hydrocarbon losses, compared to conventional gas conditioning processes.